The proposed research is part of a long-term series of studies on primate behavior, social organization, and population ecology, centered on the yellow baboons of the Masai-Amboseli Game Reserve, Kenya. Current research projects include: (1) Demography and group dynamics under changing ecological conditions; (2) Foraging strategies and selective feeding as ways of meeting nutritional requirements, with emphasis on the role of malnutrition in infant mortality; (3) Effects of dominance status and stability on differential reproduction and parasite loads; (4) Infant development and maternal care, with particular emphasis on the mother's contribution as a limited resource for the survival and welfare of the infant; (5) mathematical models of interaction processes.